The Cincinnatian (Katian) of the Cincinnati Tri-State area is widely regarded as one of the most fossiliferous sections known (Meyer and Davis, Reference Meyer and Davis2009). Echinoderms from these strata include well-described asteroids, crinoids, cyclocystoids, edrioasteroids, glyptocystoids, mitrates, and ophiuroids. John Pope discovered a partially articulated echinoderm in float from the Fairview Formation that does not correspond to any known Cincinnatian echinoderm. Although mentioned in Ubaghs (Reference Ubaghs and Moore1966, as a presumable personal communication from Pope, 1960), Haude and Langenstrassen (Reference Haude and Langenstrassen1976), Reich (Reference Reich2001), and Reich and Haude (Reference Reich and Haude2004), this specimen at the Cincinnati Museum Center (CMCPIP 51316) has neither been described nor illustrated; yet, these authors attributed it to Volchovia Hecker, Reference Hecker1938 in the Class Ophiocistioidea. Questions swirl around this fossil: what is its complete morphology; does it belong to Volchovia; whether or not it can be assigned to Volchovia, is it an ophiocistioid? The first step to understand this enigmatic echinoderm is to illustrate and describe the specimen, which is the objective of this note.

The specimen in question was collected in 1957 from the upper part of the Fairmount Member, Fairview Formation (Ordovician, Katian) in the Emming Street Quarry, Cincinnati, Ohio (this information is recorded on the specimen label). The morphologies of Cincinnatian echinoderms are typically well understood, and none of these has plating similar to Volchovia, except perhaps CMCIP 51316. Volchovia is reconstructed as having a dome-shaped test with pointed marginal plates (yielding a periphery with a serrated appearance) and central plates of variable sizes and shapes. The periproct and a sutural pore between two posterior marginal plates are also present on the aboral test surface of Volchovia (Ubaghs, Reference Ubaghs and Moore1966, fig. 135).

CMCIP 51316 is an incomplete, partially articulated specimen interpreted to be approximately half of the outer rim of a specimen and thought to have been subcircular in outline (Fig. 1.2). The specimen is ~11 mm long, ~8 mm wide, and has a dome-shaped test (Fig. 1.1). It is primarily formed of thin marginal plates that are of different sizes. The abaxial (outer) edge of the specimen is serrated because the outer edge of each marginal plate ends in a point (Fig. 1.2, 1.3). One large plate is interpreted to be a plate from the central portion of the specimen. Perhaps much smaller polygonal plates from the central portion are present, but it is unclear whether these smaller plates belong to this specimen or if they are part of the matrix in which this specimen was buried. No evidence for a periproct or other opening is present. Different sized marginal plates distinguish this specimen from reconstructions of Volchovia (Hecker, Reference Hecker1938, Reference Hecker1940; Ubaghs, Reference Ubaghs and Moore1966).

Figure 1. Volchovia? sp. from the Fairview Formation (Katian); CMCIP 51316, scale bars 2.5 mm. (1) Lateral view of test, marginal plates projecting out of the photograph (note domed structure of test), specimen coated with ammonium chloride; (2) aboral view of specimen, coated with ammonium chloride; (3) camera lucida drawing of preserved plating.

Notes from echinoderm workers who have examined this specimen expressed varying opinions about its systematic placement but urged its illustration. Thus, this specimen is illustrated for the first time. As noted, the outer rim of plates is not identical to either V. mobilis Hecker, Reference Hecker1938 or V. norvegica Regnéll, Reference Regnéll1948. The marginal plates are less regular in size and shape than those in V. norvegica, V. volborthi Hecker, Reference Hecker1938, and V. mobilis. CMCIP 51316 is also smaller than specimens of V. norvegica (50–70 mm), V. mobilis (60–70 mm), and V. volborthi (80–90 mm). Despite these differences, the morphology of CMCIP 51316 is more similar to these taxa than to any other Cincinnatian echinoderm.

If this Katian specimen is a Volchovia, it would also be the stratigraphically youngest of the species mentioned above. Volchovia mobilis (Volkhov–Kunda Baltic Regional Stages, Estonia) is Dapingian–early Darriwilian, V. volborthi (Kunda Baltic Stage, Estonia) is Darriwilian, and V. norvegica (Lysaker Member, Huk Formation, Norway) is Darriwilian (Kröger, Reference Kröger2012). Furthermore, if specimen CMCIP 51316 is determined to be Volchovia, it would prove to be the first definitive occurrence of this genus (and the family Volchoviidae Hecker, Reference Hecker1938) outside of Baltica (Lefebvre et al., Reference Lefebvre, Sumrall, Shroat-Lewis, Reich, Webster, Hunter, Nardin, Rozhnov, Guensburg, Touzeau, Noailles, Sprinkle, Harper and Servais2013).

Until the morphology of this unusual echinoderm is more fully understood, we cannot determine whether this enigmatic echinoderm belongs to Volchovia. Thus, we refer to this fossil, herein, as a volchoviid-like echinoderm.